Volcanic Source Change Triggers Divergent Climatic Responses across the Guadalupian–Lopingian Transition in Eastern South China

Volcanism is a primary driver of climate change over geological timescales, yet its effects are highly variable and depend critically on eruption style, magnitude, and tectonic setting. Large Igneous Provinces (LIPs) are often linked to greenhouse warming due to massive CO2 emissions, whereas sustained continental arc volcanism can influence long-term climate cycles by modulating atmospheric CO2 levels. The Guadalupian–Lopingian (G–L) transition (~260 Ma) presents a unique natural laboratory to investigate these differential impacts, as it witnessed the demise of the Late Paleozoic Ice Age, significant biotic turnover, and the concurrent eruptions of the Emeishan Large Igneous Province (ELIP) and the South China continental arc. Distinguishing the relative climatic roles of these coexisting volcanic systems, however, has remained a major challenge. Here, we present an integrated multi-proxy study (including geochronology, geochemistry, mercury cycling proxies, and carbon isotopes) of the Yinpingshan section (South China), which recorded both volcanic sources. Our results document a clear volcanic source transition during the G–L interval. Provenance analysis using tectonic discrimination diagrams reveals a shift from arc-dominated to LIP-dominated volcanism. This transition is marked by a profound decoupling between volcanic mercury deposition and climatic response. Intense mercury anomalies (Hg/TOC > 200 ppb/wt%), likely from proximal continental arc volcanism, show minimal carbon isotope excursions, indicating a limited climatic impact. In contrast, subsequent weaker ELIP-related mercury anomalies (Hg/TOC ≈ 80 ppb/wt%) coincide with a significant negative δ13Corg excursion of up to -2‰ and evidence of warming, implying massive CO2 emissions that overwhelmed the global carbon cycle. Following the peak volcanic activity, enhanced weathering and carbon burial likely contributing to CO2drawdown and post-volcanic cooling. Our findings demonstrate that volcanic setting and scale, not merely the presence of volcanism, governed climatic impact. While regional arc volcanism can produce strong local sedimentary Hg signals, it may not drive global climate change. Conversely, LIPs, due to their immense scale and specific degassing styles, are potent drivers of major global environmental and climatic transitions. This study provides a new framework for understanding volcanic forcing mechanisms, emphasizing that the type and scale of volcanism are critical determinants of its Earth system impact during this critical period in Earth's history.